src/system/libroot/posix/pthread/pthread_spinlock.c

   1 /*
   2  * Copyright 2010, Lucian Adrian Grijincu, lucian.grijincu@gmail.com.
   3  * Distributed under the terms of the MIT License.
   4  */
   5
   6
   7 #include <pthread.h>
   8
   9 #include <arch_cpu_defs.h>
  10
  11 #include "pthread_private.h"
  12
  13
  14 #define UNLOCKED        0
  15 #define LOCKED          1
  16
  17
  18 int
  19 pthread_spin_init(pthread_spinlock_t* lock, int pshared)
  20 {
  21         // This implementation of spinlocks doesn't differentiate
  22         // between spin locks used by threads in the same process or
  23         // between threads of different processes.
  24
  25         lock->lock = UNLOCKED;
  26         return 0;
  27 }
  28
  29
  30 int
  31 pthread_spin_destroy(pthread_spinlock_t* lock)
  32 {
  33         return 0;
  34 }
  35
  36
  37 int
  38 pthread_spin_lock(pthread_spinlock_t* lock)
  39 {
  40         while (atomic_test_and_set((int32*)&lock->lock, LOCKED, UNLOCKED)
  41                         == LOCKED) {
  42                 SPINLOCK_PAUSE(); // spin
  43                         // TODO: On UP machines we should thread_yield() in the loop.
  44         }
  45         return 0;
  46 }
  47
  48
  49 int
  50 pthread_spin_trylock(pthread_spinlock_t* lock)
  51 {
  52         if (atomic_test_and_set((int32*)&lock->lock, LOCKED, UNLOCKED) == LOCKED)
  53                 return EBUSY;
  54         return 0;
  55 }
  56
  57
  58 int
  59 pthread_spin_unlock(pthread_spinlock_t* lock)
  60 {
  61         lock->lock = UNLOCKED;
  62         return 0;
  63 }